Ceramic microsphere green body as well as preparation method, system and application thereof

Abstract

The invention relates to a ceramic microsphere green body and a preparation method, system and application thereof.The preparation method comprises the following steps that 1, water-based ceramic slurry is injected into a flowing oil phase, ceramic slurry liquid drops are cut into tiny slurry liquid drops through turbulent flow shearing, and meanwhile the tiny slurry liquid drops are formed through the surface tension effect of the ceramic slurry and the oil phase interface; the slurry liquid drops are kept spherical in the oil phase; (2) enabling the catalyst dissolved in the oil phase to be in contact with the slurry liquid drops so as to cure the gel on the outer surfaces of the slurry liquid drops, and meanwhile, carrying out heating treatment so as to cure the gel in the slurry liquid drops, thereby obtaining microspheres; (3) collecting the microspheres, cleaning, drying and discharging glue to obtain a ceramic microsphere green body; the ceramic slurry comprises the following components: a hydrogel monomer, a cross-linking agent, ceramic powder, a dispersing agent, an initiator and water. Compared with the prior art, the method has the advantages of high degree of sphericity of the microsphere green body, uniform material, high forming efficiency, and the like, and is particularly suitable for batch production.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic preparation, and in particular to a ceramic microsphere green body and a preparation method, system and application thereof. Background Art

[0002] As a versatile, high-performance material, ceramic microspheres are widely used in numerous high-tech and industrial fields due to their excellent physical and chemical properties (such as high strength, high and low temperature resistance, low density, and acid and alkali corrosion resistance). Formation of ceramic microspheres is a key step in the production process. Currently, the main forming methods include spray granulation, ball rolling, clay kneading, titration gelation, droplet jet gelation, and microfluidic gelation.

[0003] The spray granulation method is to disperse the ceramic slurry into spherical droplets with an atomizer and form them by hot air drying. The process is simple and efficient, but the diameter of the formed microspheres is difficult to control, the sphericity is poor, and holes often appear inside the green body. The rolling ball method is to add water or other binding liquid to the ceramic powder while rolling it in a drum to make it bond into balls. The equipment is simple and efficient. It is the most widely used process at present, but the formed microspheres will have uneven material (the cross-section microstructure shows an annual ring shape), and the ball quality is relatively poor. The quality of the ceramic clay is poor, and it is difficult to form microspheres with a diameter of less than 0.1mm; the clay rubbing method first uses extrusion molding to shape the ceramic clay into clay strips, cuts the clay strips into segments into particles and then rolls them into balls. Due to the large amount of organic matter in the ceramic clay that assists in molding, the density of the molded green body is low, which is not suitable for ceramic materials with high requirements for green body density. At the same time, it is also difficult to form microspheres with a diameter of less than 0.1mm; the titration gel method drips the ceramic slurry into a liquid that is not soluble in it, and the slurry droplets are spherical through the surface tension of the liquid. The microfluidic gel method uses a shear force generated by a laminar flow of a liquid immiscible with the slurry to disperse the slurry into microsphere droplets of uniform size. The gel is then solidified into microspheres, resulting in a sphere-forming process. This method has a very high sphericity and can form nano-sized microspheres. However, the microfluidic gel method uses a small microchannel size (smaller than the diameter of the formed microspheres) to generate a very small flow rate, resulting in a low slurry forming efficiency.

[0004] In summary, in the molding of ceramic microsphere green bodies, the process that can meet the requirements of high-quality microsphere green body preparation such as good sphericity and uniform material still needs to adopt the wet molding principle, namely the titration gel method, the droplet jet gel method and the microfluidic gel method. These methods all require the slurry to flow through microchannels to control the size of the microspheres, including invention patents (ZL202410649728.0, ZL 202410666517.8). The smaller the size of the molded microspheres, the easier it is to cause clogging of the microchannels and the dispersion screen, affecting production efficiency. Although ZL 202410649728.0 has improved the molding method and can form microspheres without the help of microchannels, which will not cause clogging of the microchannels, it is usually necessary to control the size of the molded microspheres through screening. This will cause clogging problems in actual operation. That is, when the size of the dispersed microspheres is close to the mesh size of the sieve, the microspheres will be stuck in the mesh, causing mesh clogging and affecting the sustainability of the process. On the other hand, in the process of preparing microspheres, this technology requires the addition of sodium alginate and curing agent Ca to the ceramic powder. 2+ 、Ba 2+ 、Sr 2+ Insoluble salts of these metal cations (Na + , Ca 2+ 、Ba 2+ 、Sr 2+ ) cannot be eliminated in the subsequent degumming treatment, that is, impurity elements are introduced into the microsphere body, which not only affects the performance of the ceramic microspheres, but also limits their application in the field of high-purity grinding media. Summary of the Invention

[0005] The purpose of the present invention is to provide a ceramic microsphere green body and its preparation method, system and application, which have high production efficiency and good stability, and the diameter of the spheres can be varied in the range of 0.01mm to 1mm.

[0006] The purpose of the present invention can be achieved by the following technical solution: A method for preparing ceramic microsphere green body, comprising the following steps:

[0007] (1) Injecting water-based ceramic slurry into a flowing oil phase, dividing the ceramic slurry droplets into tiny slurry droplets through turbulent shearing, and at the same time, using the surface tension at the interface between the ceramic slurry and the oil phase, keeping the slurry droplets spherical in the oil phase;

[0008] (2) The catalyst dissolved in the oil phase contacts the slurry droplets to solidify the gel on the outer surface of the slurry droplets, and simultaneously heats the slurry droplets to solidify the gel inside the slurry droplets, thereby obtaining slurry microspheres;

[0009] (3) collecting the slurry microspheres, washing, drying, and debinding to obtain ceramic microsphere green bodies;

[0010] The ceramic slurry comprises the following components: hydrogel monomer, cross-linking agent, ceramic powder, dispersant, initiator and water.

[0011] Preferably, the ceramic slurry comprises the following components: hydrogel monomer, cross-linking agent, ceramic powder, dispersant, initiator, binder and water.

[0012] Further preferably, the hydrogel monomer includes acrylamide, methacrylamide or N-hydroxymethyl acrylamide.

[0013] More preferably, the hydrogel monomer comprises acrylamide.

[0014] Further preferably, the cross-linking agent comprises N,N'-methylenebisacrylamide.

[0015] Further preferably, the ceramic powder includes silicon nitride ceramic powder, silicon carbide ceramic powder, aluminum oxide ceramic powder, and zirconium oxide ceramic powder.

[0016] Further preferably, the dispersant includes ammonium polyacrylate or ammonium citrate.

[0017] More preferably, the dispersant comprises ammonium polyacrylate.

[0018] Further preferably, the initiator comprises ammonium persulfate.

[0019] Further preferably, the binder includes polyvinyl alcohol and lignin.

[0020] Further preferably, the binder is added in an amount of 0.5 wt% to 2 wt% in the ceramic slurry.

[0021] Preferably, the ceramic slurry has a solid content of more than 45 vol% and a slurry viscosity of less than 10000 mPa·s.

[0022] Preferably, the method for preparing the ceramic slurry comprises the following steps: dissolving a hydrogel monomer and a cross-linking agent in water to prepare a premix, adding ceramic powder and a dispersant, and adding an initiator after ball milling.

[0023] Preferably, the oil phase includes one or more of kerosene, motor oil, liquid paraffin, and silicone oil.

[0024] Preferably, the catalyst is a catalyst that can be dissolved in the oil phase and accelerates the decomposition of the initiator in the ceramic slurry into free radical ions that initiate the gel reaction.

[0025] More preferably, the catalyst is N,N,N,N-tetramethylethylenediamine.

[0026] Preferably, a surfactant is added to the oil phase.

[0027] More preferably, the surfactant includes sorbitan fatty acid and polyoxyethylene fatty alcohol ether.

[0028] More preferably, the added amount of the surfactant is 0.5 wt% to 5 wt% of the oil phase.

[0029] Preferably, the heating treatment temperature is above 60°C.

[0030] Preferably, the method for preparing ceramic microsphere green body comprises the following steps:

[0031] S1: Dissolve the hydrogel monomer and cross-linking agent in water to prepare a premix, add ceramic powder and dispersant, and prepare slurry A after ball milling;

[0032] S2: Before slurry A is injected into the oil phase, it is uniformly mixed with the initiator in the pipeline through a static mixing tube to obtain a water-based ceramic slurry;

[0033] S3: Inject the ceramic slurry into the flowing oil phase, use a turbulence generator to generate turbulence in the oil phase pipeline, and split the ceramic slurry droplets into tiny slurry droplets through turbulent shear. At the same time, with the help of the surface tension at the interface between the ceramic slurry and the oil phase, the slurry droplets are kept spherical in the oil phase;

[0034] S4: The catalyst dissolved in the oil phase contacts the slurry droplets to cause the gel on their outer surfaces to solidify, and simultaneously heats the slurry droplets to cause the gel inside to solidify, thereby obtaining microspheres;

[0035] S5: After collecting the microspheres, they are cleaned, dried, and debonded to obtain ceramic microsphere green bodies.

[0036] Further preferably, in step S3, the ceramic slurry is injected into the oil phase pipeline.

[0037] In the present invention, a water-based ceramic slurry containing a monomer and a cross-linking agent is mixed with an initiator and then injected into an oil phase pipeline. The ceramic slurry is sheared into tiny spherical droplets by utilizing the artificial turbulence generated in the pipeline and the surface tension of the oil-water interface. A catalyst dissolved in the oil phase is then brought into contact with the slurry droplets to cause their outer surfaces to gel and solidify. Simultaneously, a heat treatment is performed to solidify the gel inside the slurry droplets, ensuring that they can better maintain their spherical shape. After collection, they are cleaned, dried, and debinded to obtain ceramic microsphere green bodies.

[0038] A system used in the above-mentioned method for preparing ceramic microsphere green bodies includes a slurry pushing device for conveying ceramic slurry and an oil phase circulation passage for conveying oil phase;

[0039] The slurry pushing device is connected to the oil phase circulation passage, and the oil phase circulation passage is provided with a turbulence generator, a ball forming device, a ball collecting pipe and a ball collecting bottle.

[0040] Further preferably, the slurry pushing device includes a ceramic slurry injector, an initiator injector, a syringe pump, a static mixing tube and a constant temperature box;

[0041] The ceramic slurry injector and initiator injector are connected to the static mixer through injection pumps respectively. The static mixer is connected to the oil phase circulation path. The ceramic slurry injector, initiator injector, injection pump and static mixing tube are all arranged in a constant temperature box.

[0042] More preferably, the thermostat is used to maintain the temperature of the slurry pushing device between 15°C and 20°C.

[0043] Further preferably, the input end of the ball forming device is connected to the turbulence generator and the slurry pushing device, and the output end is connected to the ball collecting pipe and the ball collecting bottle in sequence.

[0044] More preferably, a heating sleeve is provided on the outside of the ball collecting tube.

[0045] Preferably, the heating sleeve is a heating water sleeve, the ball collecting bottle is arranged in a water bath, and the water bath is connected to the heating water sleeve.

[0046] More preferably, the length of the ball collecting tube is more than 1 m.

[0047] More preferably, the ball collecting tube is arranged vertically, and the ball collecting bottle is arranged below the ball collecting tube.

[0048] Preferably, the ball-forming device is a hollow circular tube, which is coaxially connected to the output end of the turbulence generator and vertically connected to the output end of the slurry pushing device.

[0049] Further preferably, the tube diameter of the pelletizing device is 1-3 mm and the length is 100 to 500 mm.

[0050] Further preferably, the inner wall of the spheroidizing device is treated with a hydrophobic coating.

[0051] In the present invention, the water-based ceramic slurry can be prevented from adhering to the inner wall of the pipe by hydrophobic treatment of the inner wall of the pelletizing device.

[0052] More preferably, the water droplet contact angle of the inner wall of the spheroidizing device is greater than 90°, preferably greater than 150°.

[0053] Further preferably, the ball-forming device is arranged horizontally, and is vertically connected to the output end of the slurry pushing device from above.

[0054] Preferably, the oil phase circulation passage is further provided with an oil phase tank and an oil phase driving pump.

[0055] Preferably, the slurry pushing device is connected to the oil phase circulation passage through an injection needle.

[0056] The present invention can adjust the size of the formed ceramic microsphere green body by adjusting the needle size and the oil phase turbulence state. The needle size is positively correlated with the size of the formed ceramic microsphere green body, and the turbulence intensity is negatively correlated with the size of the formed ceramic microsphere green body.

[0057] Preferably, the turbulence generator is a pulse turbulence generator or a tubular turbulence generator.

[0058] In the present invention, the pulse turbulence generator throttles the oil phase pipeline at a certain frequency through the pulse valve, changes the flow velocity of the oil phase along the axial direction of the pipeline to create turbulence.

[0059] Tubular turbulence generators create turbulence by designing the pipeline structure, such as changing a round tube into a square tube, changing the tube diameter, or adding fins to the inner wall of the tube, and utilizing the flow velocity difference of the oil phase along the tube path.

[0060] A ceramic microsphere green body is prepared by the above preparation method and has a diameter ranging from 0.01 mm to 1 mm.

[0061] An application of the ceramic microsphere green body in the field of grinding media and thermal conductive fillers.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] 1. The present invention provides a method and apparatus for forming ceramic microsphere green bodies by turbulent shear gel. The green bodies have high sphericity, uniform material, and high forming efficiency, and are particularly suitable for mass production.

[0064] 2. The present invention mixes a water-based ceramic slurry containing a monomer and a cross-linking agent with an initiator and injects it into the oil phase pipeline. The ceramic slurry is sheared into tiny spherical droplets by utilizing the artificial turbulence generated in the pipeline and the surface tension of the oil-water interface. Compared with mechanical stirring to shear and disperse the slurry liquid phase to obtain microsphere droplets and then control the size through a screen, there is no risk of blockage and it can operate continuously and stably.

[0065] 3. The present invention does not require the ceramic slurry to flow through microchannels to control the size of the microspheres, which reduces the slurry fluidity requirements. Ceramic slurries with higher solid content can be used to reduce the shrinkage of the green body during the drying process and avoid the deterioration of sphericity.

[0066] 4. The present invention has a wide range of spherical sizes. By adjusting the turbulence generator to form turbulence of different scales in the oil phase, the size of the formed microspheres can be controlled. The diameter of the spherical microspheres can vary within the range of 0.01mm to 1mm.

[0067] 5. The ceramic microsphere green body device provided by the present invention has a simple structure, high production efficiency and good stability.

[0068] 6. In the process of preparing microspheres, no Na+ , Ca 2+ 、Ba 2+ 、Sr 2+ Insoluble salts such as iodine and iodine are beneficial to their application in the field of high-purity grinding media. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 It is a schematic diagram of the principle of turbulent shearing into balls;

[0070] Figure 2 Schematic diagram of the structure of the ceramic microsphere green body preparation system used in the embodiment of the present invention;

[0071] In the figure: 1- turbulence generator, 2- spheroidizing device, 3- spheroid collecting tube, 4- spheroid collecting bottle, 5- ceramic slurry injector, 6- initiator injector, 7- syringe pump, 8- static mixing tube, 9- constant temperature box, 10- oil phase tank, 11- oil phase driving pump, 12- water bath, 13- water bath driving pump, a- oil phase, b- ceramic slurry. DETAILED DESCRIPTION

[0072] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0073] A method for forming ceramic microsphere green bodies by turbulent shear gelation comprises the following steps: 1) preparing a ceramic slurry, dissolving a hydrogel monomer and a cross-linking agent in water to form a premixed solution, adding ceramic powder and a dispersant, and preparing the ceramic slurry by ball milling; 2) before the slurry is injected into an oil phase, uniformly mixing the slurry with an initiator in the pipeline through a static mixing tube; 3) injecting the slurry into a flowing oil phase, artificially generating turbulence in the oil phase pipeline using a turbulent flow generator, and dividing the slurry droplets into tiny slurry droplets through turbulent shearing. At the same time, the slurry droplets maintain a spherical shape in the oil phase (e.g., by means of surface tension at the interface between the water-based slurry and the oil phase) by virtue of the surface tension at the interface between the water-based slurry and the oil phase. Figure 1 ); 4) after the slurry is sheared into spherical droplets, the catalyst dissolved in the oil phase contacts the slurry droplets to solidify the gel on their outer surface, and simultaneously heats the slurry droplets to solidify the gel inside the droplets, thereby increasing the strength of the green body and ensuring that it can better maintain its spherical shape; 5) after collection, the green body is obtained through washing, drying, and debinding.

[0074] As a preferred technical solution, in addition to the hydrogel monomer and the cross-linking agent, a binder such as polyvinyl alcohol, lignin, etc. is preferably added, preferably in an amount of 0.5wt% to 2wt%, to further increase the strength of the ceramic microsphere body.

[0075] As a preferred technical solution, the solid content of the ceramic slurry is preferably above 45 vol% to reduce the shrinkage of the microsphere body during drying and prevent large deformation. The slurry viscosity is preferably below 10,000 mPa·s to ensure that it has a certain fluidity and is easy to shear and split.

[0076] As a preferred technical solution, the oil phase can be kerosene, motor oil, liquid paraffin, silicone oil, etc., or they can be mixed with each other. It is preferred to add a surfactant, such as sorbitan fatty acid, polyoxyethylene fatty alcohol ether, etc., in an amount of 0.5wt% to 5wt%, to play a dispersing role and effectively reduce the adhesion of the microspheres in the oil phase.

[0077] As a preferred technical solution, the catalyst refers to a catalyst that is soluble in the oil phase and accelerates the decomposition of the initiator into free radical ions that initiate the gelation reaction, preferably N,N,N,N-tetramethylethylenediamine.

[0078] As a preferred technical solution, heat treatment refers to heating the oil phase to a temperature of above 60°C.

[0079] A ceramic microsphere green body forming device, such as Figure 2 As shown, it includes a slurry pushing device, an oil phase circulation path, a turbulence generator 1, a ball forming device 2, a ball collecting pipe 3 and a ball collecting bottle 4. The slurry pushing device is composed of a precision injection pump 7, an injector (ceramic slurry injector 5, initiator injector 6), a static mixing pipe 8 and a constant temperature box 9, which realizes uniform mixing of the slurry and the initiator and avoids premature solidification of the slurry and the initiator due to excessively high ambient temperature after mixing; the oil phase circulation path refers to the oil phase from the oil phase storage bottle (oil phase tank 10) through the oil pump (oil phase drive pump 11) pumped through the turbulence generator 1, the ball forming device 2, the ball collecting pipe 3 and the ball collecting bottle 4 and then returned to the oil phase storage bottle; the turbulence generator 1 , which changes the radial and / or axial flow velocity of the oil phase when it flows in the pipeline through means such as pulse valves and pipeline structure design, so as to generate turbulence in the flowing oil phase, and is placed before the ball-forming device 2; the ball-forming device 2 allows the slurry to enter the oil phase and be subjected to the turbulent shearing effect therein to form tiny spherical droplets; the ball-collecting tube 3 has a double-layer tube structure, and after the slurry forms spherical droplets in the oil phase, it enters the inner tube together with the oil phase. A heating water jacket is provided outside the inner tube, and hot water is introduced to heat the slurry droplets and the oil phase in the inner tube; the slurry droplets in the ball-collecting tube 3 naturally fall to the ball-collecting bottle 4 under the action of gravity, and the ball-collecting bottle 4 is heated in a water bath to further promote the gelation of microspheres.

[0080] As a preferred technical solution, the thermostat maintains the temperature of the entire slurry pushing device assembly between 15°C and 20°C.

[0081] As a preferred technical solution, in the spheroidizing device, the slurry preferably enters the oil phase through an injection needle. The size of the formed ceramic microsphere green body can be adjusted by adjusting the needle size and the turbulent state of the oil phase. The diameter of the spheres can vary in the range of 0.01 mm to 1 mm.

[0082] As a preferred technical solution, the length of the ball collecting tube is preferably more than 1m, so that the microsphere droplets have enough falling time, so that their surface and subsurface are fully solidified and have a certain strength, ensuring that they will not deform when they fall into the ball collecting bottle and collide with each other.

[0083] As a preferred technical solution, the ball collecting bottle 4 is set in the water bath 12, the water bath 12 is connected to the heating water jacket, and the water is driven by the water bath pump 13 to realize the circulation of water between the water bath 12 and the heating water jacket.

[0084] The present invention will be further described below with reference to specific examples. These examples are intended to illustrate the present invention only and are not intended to limit the scope of the invention. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise stated, all percentages and parts are by weight.

[0085] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods and materials similar or equivalent to those described herein can be applied to the methods of the present invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0086] Example 1

[0087] (1) Silicon nitride ceramic powder ratio (mass ratio): α-Si3N4 powder: Al2O3: Y2O3 = 92:4:4;

[0088] (2) Ceramic slurry ratio (mass ratio): silicon nitride ceramic powder: water: acrylamide: N,N'-methylenebisacrylamide: polyvinyl alcohol = 73:23:3:0.3:0.7, and polyammonium acrylate (PAA-NH4) dispersant was added at a rate of 0.04% of the weight of the ceramic powder. After ball milling, silicon nitride ceramic slurry was obtained, and the viscosity was tested to be 3000 mPa·s;

[0089] (3) Initiator solution: aqueous solution of ammonium persulfate, with a mass concentration of 4%;

[0090] (4) Oil phase ratio (mass ratio): kerosene: N,N,N,N-tetramethylethylenediamine: fatty acid sorbitan = 94:5:1;

[0091] (5) Slurry pushing speed: 0.5 mL / min, initiator solution pushing speed: 0.05 mL / min, the slurry temperature is maintained at 18 °C before passing through the needle into the oil phase by a constant temperature box, the inner diameter of the needle is 0.6 mm, the oil phase flow rate is 50 mL / min, a pulse valve is used to create turbulence, throttling once every 0.5 s, combined with the inner finned tube to create turbulence, the slurry is sheared into tiny droplets, which enter the collecting tube with the oil phase, and the N,N,N,N-tetramethylethylenediamine dissolved in the oil phase in the collecting tube contacts the slurry droplets, causing the surface gel to solidify;

[0092] (6) By pumping hot water from the water bath into the outer water jacket of the collecting tube, the outer water jacket is heated and kept warm at 60°C to further promote the solidification of the slurry droplets;

[0093] (7) The slurry droplets fall into the ball collecting bottle through the ball collecting tube and continue to be heated and kept warm in a water bath until the inside is completely solidified;

[0094] (8) The fully solidified ceramic microspheres were cleaned and dried, and finally placed in a debinding furnace at 580°C to remove organic matter inside the blank, thereby obtaining silicon nitride ceramic microsphere green bodies that can be directly sintered. The size range is 0.1 mm to 0.3 mm, and the sphericity is 0.99 (10 microspheres were randomly selected, and the minimum and maximum diameters were measured, and the average value of the ratio was obtained by dividing the two).

[0095] Example 2

[0096] (1) Ceramic slurry ratio (mass ratio): alumina ceramic powder: water: acrylamide: N,N'-methylenebisacrylamide: polyvinyl alcohol = 83:13:3:0.3:0.7. At the same time, polyammonium acrylate (PAA-NH4) dispersant was added in an amount of 0.04% by weight of the ceramic powder. After ball milling, alumina ceramic slurry was obtained, and the viscosity value was tested to be 4500 mPa·s.

[0097] (2) Initiator solution: aqueous solution of ammonium persulfate, with a mass concentration of 4%;

[0098] (3) Oil phase ratio (mass ratio): kerosene: N,N,N,N-tetramethylethylenediamine: fatty acid sorbitan = 94:5:1;

[0099] (4) Slurry pushing speed: 0.5 mL / min, initiator solution pushing speed: 0.05 mL / min, the slurry temperature is maintained at 18 °C before passing through the needle into the oil phase by a constant temperature box, the inner diameter of the needle is 0.8 mm, the oil phase flow rate is 50 mL / min, a pulse valve is used to create turbulence, throttling once every 0.5 s, combined with the inner finned tube to create turbulence, the slurry is sheared into tiny droplets, which enter the collecting tube with the oil phase, and the N,N,N,N-tetramethylethylenediamine dissolved in the oil phase in the collecting tube contacts the slurry droplets, causing the surface gel to solidify;

[0100] (5) By pumping hot water from the water bath into the outer water jacket of the collecting tube, the tube is heated and kept warm at 60°C to further promote the gel solidification of the slurry droplets;

[0101] (6) The slurry droplets fall into the ball collecting bottle through the ball collecting tube, and continue to be heated and kept warm in a water bath to completely solidify the interior;

[0102] (7) The fully solidified ceramic microspheres are cleaned and dried, and finally placed in a debinding furnace at 580°C to remove organic matter inside the green body, thereby obtaining alumina ceramic microsphere green bodies that can be directly sintered, with a size range of 0.3 mm to 0.8 mm and a sphericity of 0.98.

[0103] Example 3

[0104] (1) Zirconia ceramic powder ratio (mass ratio): ZrO2 powder: Y2O3 = 95.5:4.5;

[0105] (2) Ceramic slurry ratio (mass ratio): zirconia ceramic powder: water: acrylamide: N,N'-methylenebisacrylamide: polyvinyl alcohol = 84:12:3:0.3:0.7. At the same time, polyammonium acrylate (PAA-NH4) dispersant was added in an amount of 0.04% by weight of the ceramic powder. After ball milling, zirconia ceramic slurry was obtained, and the tested viscosity value was 1500 mPa·s.

[0106] (3) Initiator solution: aqueous solution of ammonium persulfate, with a mass concentration of 4%;

[0107] (4) Oil phase ratio (mass ratio): kerosene: N,N,N,N-tetramethylethylenediamine: fatty acid sorbitan = 94:5:1;

[0108] (5) Slurry pushing speed: 0.5 mL / min, initiator solution pushing speed: 0.05 mL / min, the slurry temperature is maintained at 18 °C before passing through the needle into the oil phase by a constant temperature box, the inner diameter of the needle is 0.3 mm, the oil phase flow rate is 50 mL / min, a pulse valve is used to create turbulence, throttling once every 0.5 s, combined with the inner finned tube to create turbulence, the slurry is sheared into tiny droplets, which enter the collecting tube with the oil phase, and the N,N,N,N-tetramethylethylenediamine dissolved in the oil phase in the collecting tube contacts the slurry droplets, causing the surface gel to solidify;

[0109] (6) By pumping hot water from the water bath into the outer water jacket of the collecting tube, the outer water jacket is heated and kept warm at 60°C to further promote the solidification of the slurry droplets;

[0110] (7) The slurry droplets fall into the ball collecting bottle through the ball collecting tube and continue to be heated and kept warm in a water bath until the inside is completely solidified;

[0111] (8) The completely solidified ceramic microspheres are cleaned and dried, and finally placed in a debinding furnace at 580°C to remove organic matter inside the green body, thereby obtaining green zirconia ceramic microspheres with a size range of 0.05 mm to 0.1 mm and a sphericity of 0.99.

[0112] Example 4

[0113] (1) Ceramic slurry ratio (mass ratio): silicon carbide ceramic powder: water: acrylamide: N,N'-methylenebisacrylamide: polyvinyl alcohol = 83:13:3:0.3:0.7. At the same time, polyammonium acrylate (PAA-NH4) dispersant was added at an amount of 0.04% of the weight of the ceramic powder. After ball milling, silicon carbide ceramic slurry was obtained, and the test viscosity value was 2900 mPa·s;

[0114] (2) Initiator solution: aqueous solution of ammonium persulfate, with a mass concentration of 4%;

[0115] (3) Oil phase ratio (mass ratio): kerosene: N,N,N,N-tetramethylethylenediamine: fatty acid sorbitan = 94:5:1;

[0116] (4) Slurry pushing speed: 0.7 mL / min, initiator solution pushing speed: 0.07 mL / min, the slurry temperature is maintained at 18°C before passing through the needle into the oil phase by a constant temperature box, the inner diameter of the needle is 0.6 mm, the oil phase flow rate is 50 mL / min, a pulse valve is used to create turbulence, throttling once every 0.5 s, combined with the inner finned tube to create turbulence, the slurry is sheared into tiny droplets, which enter the collecting tube with the oil phase, and the N,N,N,N-tetramethylethylenediamine dissolved in the oil phase in the collecting tube contacts the slurry droplets, causing the surface gel to solidify;

[0117] (5) By pumping hot water from the water bath into the outer water jacket of the collecting tube, the tube is heated and kept warm at 60°C to further promote the gel solidification of the slurry droplets;

[0118] (6) The slurry droplets fall into the ball collecting bottle through the ball collecting tube, and continue to be heated and kept warm in a water bath to completely solidify the interior;

[0119] (7) The fully solidified ceramic microspheres are cleaned and dried, and finally placed in a debinding furnace at 580°C to remove organic matter inside the green body, thereby obtaining silicon carbide ceramic microsphere green bodies that can be directly sintered, with a size range of 0.4 mm to 0.8 mm and a sphericity of 0.97.

[0120] Comparative Example 1

[0121] (1) Silicon nitride ceramic powder ratio (mass ratio): α-Si3N4 powder: Al2O3: Y2O3 = 92:4:4;

[0122] (2) Ceramic slurry ratio (mass ratio): silicon nitride ceramic powder: water: acrylamide: N,N'-methylenebisacrylamide: polyvinyl alcohol = 73:23:3:0.3:0.7, and polyammonium acrylate (PAA-NH4) dispersant was added at a rate of 0.04% of the weight of the ceramic powder. After ball milling, silicon nitride ceramic slurry was obtained, and the viscosity was tested to be 3000 mPa·s;

[0123] (3) Initiator solution: aqueous solution of ammonium persulfate, with a mass concentration of 4%;

[0124] (4) The ceramic slurry and the initiator are mixed through a static mixing tube and then dripped into the oil phase. The oil phase ratio (mass ratio) is: kerosene: N,N,N,N-tetramethylethylenediamine: fatty acid sorbitan = 94:5:1;

[0125] (5) Using the microsphere green body preparation method ZL 202410649728.0, the slurry dropped into the oil phase is sheared into microsphere droplets by mechanically stirring the oil phase, and then the microsphere droplets dispersed in the oil phase with the surface of the initial solidification are sieved through a 60-mesh screen;

[0126] (6) After sieving, heat in a water bath at 60°C to promote gel solidification of the slurry droplets;

[0127] (7) The fully solidified ceramic microspheres were cleaned and dried, and finally placed in a debinding furnace at 580°C to remove organic matter inside the green body, thereby obtaining green silicon nitride ceramic microspheres that can be directly sintered. The size range is 0.02 mm to 0.23 mm. Some of the microspheres were broken and deformed due to being squeezed by the mesh of the screen.

[0128] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing ceramic microsphere green body, characterized in that: The following steps are involved: (1) Injecting water-based ceramic slurry into a flowing oil phase, dividing the ceramic slurry droplets into tiny slurry droplets through turbulent shearing, and at the same time, using the surface tension at the interface between the ceramic slurry and the oil phase, keeping the slurry droplets spherical in the oil phase; (2) The catalyst dissolved in the oil phase contacts the slurry droplets to solidify the gel on the outer surface of the slurry droplets, and simultaneously heats the slurry droplets to solidify the gel inside the slurry droplets to obtain microspheres; (3) collecting the microspheres, washing, drying, and debinding to obtain ceramic microsphere green bodies; The ceramic slurry comprises the following components: hydrogel monomer, cross-linking agent, ceramic powder, dispersant, initiator and water.

2. The method for preparing ceramic microsphere green body according to claim 1, characterized in that: The ceramic slurry comprises the following components: hydrogel monomer, cross-linking agent, ceramic powder, dispersant, initiator, binder and water; The hydrogel monomer includes acrylamide, methacrylamide or N-hydroxymethyl acrylamide; The cross-linking agent includes N,N'-methylenebisacrylamide; The dispersant includes ammonium polyacrylate or ammonium citrate; The initiator includes ammonium persulfate; The binder includes polyvinyl alcohol and lignin; The amount of the binder added to the ceramic slurry is 0.5wt% to 2wt%; The solid content of the ceramic slurry is above 45 vol%, and the slurry viscosity is below 10000 mPa·s.

3. The method for preparing ceramic microsphere green body according to claim 1, characterized in that: The preparation method of the ceramic slurry comprises the following steps: dissolving a hydrogel monomer and a cross-linking agent in water to prepare a premixed liquid, adding ceramic powder and a dispersant, and then ball milling and adding an initiator.

4. The method for preparing ceramic microsphere green body according to claim 1, characterized in that: The oil phase includes one or more of kerosene, engine oil, liquid paraffin, and silicone oil; The catalyst is a catalyst that can dissolve in the oil phase and accelerate the decomposition of the initiator in the ceramic slurry into free radical ions that initiate the gel reaction; A surfactant is added to the oil phase; The heating treatment temperature is above 60°C.

5. The method for preparing ceramic microsphere green body according to claim 4, characterized in that: The catalyst is N,N,N,N-tetramethylethylenediamine; The surfactant includes fatty acid sorbitan and polyoxyethylene fatty alcohol ether; The added amount of the surfactant is 0.5 wt% to 5 wt% of the oil phase.

6. A system used in the method for preparing ceramic microsphere green bodies according to any one of claims 1 to 5, characterized in that: It includes a slurry pushing device for conveying ceramic slurry and an oil phase circulation passage for conveying oil phase; The slurry pushing device is connected to an oil phase circulation passage, and the oil phase circulation passage is provided with a turbulence generator (1), a ball forming device (2), a ball collecting pipe (3) and a ball collecting bottle (4).

7. The system used in the method for preparing ceramic microsphere green bodies according to claim 6, characterized in that: The slurry pushing device comprises a ceramic slurry injector (5), an initiator injector (6), a syringe pump (7), a static mixing tube (8) and a constant temperature box (9); The ceramic slurry injector (5) and the initiator injector (6) are respectively connected to the static mixer (8) via the injection pump (7), and the static mixer (8) is connected to the oil phase circulation path. The ceramic slurry injector (5), the initiator injector (6), the injection pump (7) and the static mixing tube (8) are all arranged in a constant temperature box (9).

8. The system used in the method for preparing ceramic microsphere green bodies according to claim 6, characterized in that: The input end of the ball forming device (2) is connected to the turbulence generator (1) and the slurry pushing device, and the output end is connected to the ball collecting pipe (3) and the ball collecting bottle (4) in sequence; A heating sleeve is provided on the outside of the ball collecting tube (3); The oil phase circulation passage is also provided with an oil phase tank (10) and an oil phase driving pump (11).

9. A ceramic microsphere green body, characterized in that: The nanostructured carbon nanotubes are prepared by the preparation method according to any one of claims 1 to 8, and have a diameter in the range of 0.01 mm to 1 mm.

10. Use of the ceramic microsphere green body according to claim 9 in the fields of grinding media and thermal conductive fillers.

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